Epithelioid trophoblastic tumor with lung metastasis: A case report and literature review

Rationale: Epithelioid trophoblastic tumor (ETT) is an extremely rare variant of gestational trophoblastic neoplasms (GTNs). The biological behavior and therapeutic schedule of ETT remains to be defined which frequently poses diagnostic and therapeutic challenges. Although ETT is a relatively indolent malignancy tumor, the therapeutic efficacy and survival rate decrease significantly when presented with metastases. The lung is the most common site of ETT metastasis. Patient concerns: A 39-year-old female patient presented with irregular vaginal bleeding and slight distention pain in lower abdomen. Diagnoses: The patient was diagnosed ETT with lung metastasis after surgery and immunohistochemical staining. Interventions: A total abdominal hysterectomy plus bilateral salpingectomy and histopathology were performed. The patient received 3 cycles of etoposide, methotrexate, actinomycin-D/etoposide, cisplatin (EMA/EP) regimen chemotherapy after surgery. Due to the presence of lung metastasis, she received pulmonary lesion resection and another cycle of postoperative chemotherapy. Outcomes: The patients showed a good response to treatment initially. However, the patient did not complete the full initial treatment for family reasons and had signs of recurrence after 2.5 months. The serum β-hCG level gradually elevated and the lung imaging showed that the lesion area gradually expanded. After 15 months of follow-up, the patient declined further treatment due to a lack of presenting symptoms. Lessons: The diagnosis of ETT should be taken into consideration in patients with abnormal vaginal bleeding and low levels of β-hCG. Patients with metastatic disease should be treated with complete surgical resection and intensive combination chemotherapy to maximize the opportunity for cure. Targeted biological agents might be potential therapeutic strategies for chemotherapy-resistant or recurrent patients.


Introduction
Choriocarcinoma (CC), placental site trophoblastic tumor (PSTT), and epithelioid trophoblastic tumor (ETT) can occur after any type of pregnancy and collectively known as gestational trophoblastic neoplasms (GTNs), and the latter 2 originate from intermediate trophoblastic cells in the placental region, which are commonly called together intermediate trophoblastic tumors (ITTs). [1][4] The majority of ETTs arise in the lower uterine segment and cervix, followed by the uterine corpus. [5,6][12] It can also be found in the liver, brain, ovarian, vagina This study was supported by the Jilin Science and Technology Funds, China (Grant No. 20210204025YY), and the Health Special Project Founds of Jilin Province (Grant No. 2020SCZT042).

The authors have no conflicts of interest to disclose.
Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study.and spine, etc. [13][14][15][16][17] Unlike other GTNs, ITTs have a greater propensity for lymphatic spread. [18]Single or multiple sites of metastasis can be present.ETT exhibits similar behaviors and overlapping clinical features to PSTT, including slow growing, relatively low β-hCG concentrations, and less chemotherapy sensitive, [3,19,20] therefore, the treatment approach for both is typically identical.For ITTs, the mainstay of treatment is surgical resection which is different from other GTNs. [1,3]Herein, we report a case of intrauterine ETT with lung metastasis in a 39-year-old premenopausal woman with a systematic review of the literature.

Case report
In early July 2022, a 39-year-old, gravida 3, para 1, Chinese woman presented to our hospital with complaints of irregular vaginal bleeding for half a year and slight distention pain in lower abdomen occurred in the past 2 weeks.Ultrasound scan revealed a heterogeneous echo of the posterior wall of the uterus projecting toward the uterine cavity approximately 10.5 × 10.2 cm in size and blood flow signals can be found in periphery (Fig. 1A), which coupled with an elevated level of serum β-hCG (1031.46mIU/mL).The patient had 1 vaginal delivery 11 years ago, and 2 miscarriages 21months ago and 5 years ago, respectively.An intradermal contraceptive device was implanted in her left upper arm at a private clinic 20 months ago.A magnetic resonance imaging (MRI) scan of the pelvis showed a pelvic tumor (Fig. 1B and C), furthermore, multiple nodular hyperdensities in the right upper and middle lobe were revealed by a high-resolution computed tomography (HRCT) scan of the chest, indicating that might be distant metastasis (Fig. 1D), and there were no definite abnormalities on brain MRI.After 9 days, the blood β-hCG value was 2034.26 mlU/mL which showed an upward trend.Subsequently, the patient underwent exploratory laparotomy with total abdominal hysterectomy and bilateral salpingectomy.During the operation, a 12.0 × 10.0 × 9.0 cm sized spherically enlarged uterus was seen with compression and displacement of surrounding tissues.Gross pathologic examination revealed a 9.5 × 6.0 × 6.0cm, gray-red, friable mass with extensive necrosis within the myometrium (Fig. 2).The boundary between the mass and the myometrium was not clear.Mitotic rate was 17 per 10 high power fields and lymphovascular space invasion was identified.Immunohistochemistry staining indicated that CK(AE1/AE3) (−), P40 (partial +), p63 (local weak +), HCG (local +), hPL (local +), MUC4 (local +), Ki67 (positive rate 40%), Vimentin (−), CD10 (+), α-inhibin (−), SALL-4 (−), SMA (−), GATA3 (+).The histological and immunohistochemical features are presented in Figure 3. Postoperative diagnosis: ETT.
The patient received 3 cycles EMA-EP chemotherapy regimens after the operation, and the levels of β-hCG dropped to normal at the end of the third cycle chemotherapy.Subsequently, the patient transferred to thoracic surgery department for further diagnosis and treatment.A preoperative HRCT scan revealed multiple nodular hyperdensities in the left upper lobe as well as in the right upper and middle lobes.The largest highdensity nodule, measuring approximately 11 mm in diameter, was identified in the right upper lobe.Another 11 mm nodule in the right upper lobe exhibited an empty bubble within it (Fig. 1E  and F).She underwent the thoracoscopic wedge resection of left upper lobe, right upper and middle lobe.As expected, the histopathologic and immunochemical results were compatible with the diagnosis of ETT.Immunohistochemistry staining indicated that CK(AE1/AE3) (+), p63 (partial +), α-inhibin (focal +), HCG (−), hPL (+), Ki67 (positive rate 10%), TTF-1 (−), Napsin A (−), GATA3 (+), MUC4 (Scattered +), EMA (+), CK8/18 (+), CK5/6 (+).The histological and immunohistochemical features are presented in Figure 4.
Unfortunately, the patient declined further medical treatment due to family reasons after completing 1 cycle of EMA-EP chemotherapy regimen following lung surgery.An HRCT scan of chest indicated the presence of a pulmonary nodule (6 mm) before the fourth cycle chemotherapy regimen, whereas the followup examination conducted 2 months after the completion of chemotherapy did not reveal any definitive nodular lesion.There was irregular monitoring of the levels of serum β-hCG after discharge.During follow-up, serum β-hCG increased to 10.03 mIU/mL about 2.5 months after the last cycle of chemotherapy regimen.The patient declined the recommendation to continue treatment.The blood β-hCG value rose to 663.63 mIU/mL until 8 months after the last chemotherapy regimen.The changes in β-hCG levels are shown in Figure 5. Eleven months after the last chemotherapy regimen, the HRCT scan of chest showed multiple soft-tissue densities of both lungs under the pleura which the largest one measuring approximately  55*34 mm in size (Fig. 1G).And multiple nodular hyperdensities were revealed in both lungs which the largest one about 8 mm in diameter located in the left lower lobe (Fig. 1H).She was not a surgical candidate due to extensive metastases in her lungs.The patient remained asymptomatic at the time of reporting, and we are continuing to encourage the patient to proceed with treatment.

Discussion
ETT is an extremely rare form of GTN which arises from the chorionic-type intermediate trophoblast.It was previously reported that tumors contain unique paternal genomic element which indicated ETT was associated with prior gestational events. [21]ETT could secondary to full-term pregnancy, hydatidiform mole, ectopic pregnancy, and GTN; however, there have been also reported that nulliparous patients diagnosed ETT, likely with an undocumented spontaneous abortion. [3,22]ETT mostly presents in reproductive-aged women, but there have been reported cases of postmenopausal patients. [23,24]And the occurrence of ETT in male patients is particularly rare, only about 7 cases have been reported in the English literature to data. [25,26]he reported interval between the antecedent pregnancy and the clinical manifestation ranges from 1 week to decades. [16,27]TT has no specific symptom or sign and tends to be diagnosed by pathological assessment.Patients with ETT performed different clinical presentations which depending on the site of involvement.The majority of patients underwent abnormal vaginal bleeding, and others complained amenorrhea, abdominal pain, and abdominal bloating. [3,6]And dyspnea or hemoptysis may be found due to lung involvement.However, it is sometimes entirely asymptomatic at the time of diagnosis, especially  in patients who have extra-uterine ETT. [3,28]Unlike in patients with CC (>10,000 IU/L), the levels of serum β-hCG generally mildly elevated in patients with ETT (<2500 IU/L).Interestingly, the levels of β-hCG is persistent negative in some patients and markedly elevated β-hCG levels (>10,000 IU/L) in patients with mixed GTN which indicated β-hCG levels may not be reliable for the diagnosis and follow-up of ETT, nevertheless, β-hCG levels may be higher in advanced stage disease. [11,29]The clinical manifestations, imaging, and β-hCG levels are easily misdiagnosed as ectopic pregnancy and CC. [3,29,30]nlike CC which can be diagnosed based on clinical presentation and significantly elevated serum levels of β-hCG, ETT and PSTT are mainly diagnosed based on specific pathological evidence.Given that different treatments are recommended for each tumor, it is critical to distinguish ETT from other tumors.The diagnosis of ETT is easily delayed due to nonspecific clinical features.ETT may be confused with squamous cell carcinoma (SCC) because of its frequent involvement of the lower uterine segment, the appearance of epithelioid histologic morphology, positivity for p63 and keratins, and its eosinophilic hyaline material similar to keratin. [31]The expression of P16 is helpful to differentiate ETT and SCC, as the latter is positive whereas ETT is negative. [32]Furthermore, Ki-67 proliferative index is always high (>50%) in SCC which is usually >10% in ETT. [1,33]NA fingerprinting analysis demonstrating chimerism is a powerful diagnostic application in cases with equivocal immunohistochemistry. [34] HPV in situ hybridization may help in making the diagnosis of HPV-related cervical lesions.In clinical work, ETT may also be misdiagnosed as CC or PSTT. [35]P63 plays an essential role in differential diagnosis of ETT and PSTT, which is positive in ETT and negative in PSTT. [36]In the differentiation from CC, ETT component shows a relatively uniform population of mononuclear intermediate trophoblastic cells, however, CC is composed of a typically biphasic pattern with multinuclear syncytiotrophoblast and mononuclear cytotrophoblast. [29]C specifically expressed SALL4 which may be helpful in the differential diagnosis. [37]Moreover, HCG is focally positive in ETT but is diffusely positive in CC, and the Ki-67 proliferative index is a useful tool to distinguish ETT from CC. [19] However, ETT could coexist with PSTT and CC which makes the diagnosis and treatment more difficult. [35,38]The coexistence of CC should be considered in ITTs patients with high β-hCG levels. [29]TT is a relatively indolent malignancy tumor which the disease survival is more than 90% when there are no metastases, but it drops to 50% to 60% when there are metastases. [39,40]The treatment of ETT is predominately based on the stage of disease with some appropriate consideration of high-risk factors.ETT is more chemo-resistant compared to CC, the primary therapeutic option of ETT is complete surgical removal.][43] Sugrue et al reported the overall survival is similar regardless of minimally invasive or open abdominal hysterectomy. [44]For premenopausal women, it is not considered to conventional removal of the ovaries. [30,41]ymphadenectomy can be performed in patients, whereas it is uncertain if this improves survival. [11,45]If preoperative radiological lymph node involvement is suspected, lymph node sampling is recommended due to the potential for ETT to spread through lymphatics. [45,46]Surgical treatment combined with multipledrug chemotherapy, immunotherapy and targeted therapy should be considered during the late stage of ETT.
The International Federation of Gynecology and Obstetrics (FIGO) system could be used to stage ETT, whereas the prognostic score is not applicable. [47]Due to the characteristic of more chemo-resistant for ETT, single-agent chemotherapy is insufficient and multi-agent treatment is required for poor prognosis and/or metastatic disease. [2,48]Given the rarity of the disease and the lack of controlled trails, the optimal chemotherapy regimen for ETT remains to be defined.][50] Therefore, platinum-based regimens such as EMA/EP or paclitaxel, cisplatin/paclitaxel, etoposide are recommended chemotherapy for patients with ETT, especially those with persistently positive levels of β-hCG after surgery, metastatic lesions and are inoperable. [11,30,42,48,50]There is controversy about whether patients in stage I disease benefit from adjuvant chemotherapy.Patients with normal levels of β-hCG in stage I seem to be enough to receive surgery alone. [3,30,51]Nevertheless, it is still uncertain.][55][56][57] Besides, Yang et al suggested that the positive expression of LAG-3 was a prognostic factor for disease recurrence. [58]But the timing, type and duration of multi-agent chemotherapy are unclear.Zhang et al reported that serum β-hCG is not the only factor of chemotherapy withdrawal and follow-up monitoring, and imaging examination are more essential for ETT. [54]Additionally, different approaches to the sequencing of surgery and chemotherapy have been used, although the best approach is not clear.Here, we summarized the characteristics of uterine primary ETT with metastasis or extrauterine ETT in case reports, as shown in Table 1.In our case, the patient was treated with total abdominal hysterectomy plus bilateral salpingectomy.She received 3 cycles of EMA/EP regimen chemotherapy after surgery and the serum levels of β-hCG returned to normal.Due to the presence of lung metastasis, she received pulmonary lesion resection and 1 cycle of postoperative chemotherapy.The patients showed a good response to treatment initially.However, the initial planned 4 to 5 cycles of chemotherapy following the lung surgery were not completed due to the patient's noncompliance.Unfortunately, the disease recurred rapidly after treatment interruption.Despite our repeated attempts to encourage the patient to receive treatment upon the recurrence of the disease, the latter still refused because of the absence of symptoms.Therefore, we failed to assess the final outcomes of this treatment regimen for lung metastases in the ETT patient.
The use of high-dose chemotherapy (HDC) with peripheral blood stem cell support appears to be active in patients with refractory and relapsed disease. [64,91,92]In the study by Frijstein et al, 45% (5/11) of patients with ETT/PSTT presenting ≥ 48 months after antecedent pregnancy were in remission. [91]But they also suggested that it should consider the risk of lifethreatening complications and the emergence of new less toxic salvage therapies such as pembrolizumab before using HDC. [91,93]ince a significant amount of gestational trophoblastic tumors, including ETT, express the PD-L1 receptor, there has been reported immunotherapy using pembrolizumab as a successful treatment in ETT. [13,42,52,58,84]Pembrolizumab has been hypothesized to be a reasonable option for therapy of ETT patients with significant PD-L1 positivity and especially chemo-resistance or recurrent.Additionally, EGFR, VEGF, PD-L2, B7-H3, VISTA, LPCAT1, and CD105 were identified as potential therapeutic targets for metastatic or recurrent ETT. [10,42]ata on fertility-sparing therapy in ETT are even more scarce.There have been reported 4 patients only received lesion excision with or without chemotherapy, no signs of recurrence were found during the followup period. [38,86,94]Conversely, Davis [3] and Liu et al [49] reported 3 patients with ETT refused hysterectomy for their desire of ongoing fertility who subsequently developed recurrence or progressive disease.The delay in instigating surgical treatment may account for the recurrence and death.Given these discrepant results, the safety of fertilitysparing treatment in ETT remains uncertain.For young women who strongly desire to preserve their childbearing potential, a  Li et al [69] − Lung   fertility-sparing approach should be only for accurately selected patients after an adequate and extensive counseling.It is not suitable to preserve fertility in patients with diffuse lesions. [1]

Conclusion
ETT is a rare potentially high-risk GTN with the variability in presentation which may lead to delay in treatment.Surgery is the mainstay of treatment in ETT.For metastatic disease and localized disease with poor prognostic factors, combined surgical resection and muti-chemotherapy are recommended to maximize the opportunity for cure.However, many questions remain to be resolved regarding the optimal management of ETT.Further studies on the exploration of potentially valuable therapeutic strategies are urgently needed.More cases and data of ETT should be reported to implement the knowledge on ETT management and shape future therapies.
Second Hospital of Jilin University.a Department of Obstetrics and Gynecology, The Second Hospital of Jilin University, Changchun, Jilin, China, b Department of Orthopaedics, The Second Hospital of Jilin University, Changchun, Jilin, China, c Research Center, The Second Hospital of Jilin University, Changchun, Jilin, China.

Figure 1 .
Figure 1.Imaging findings: (A) Ultrasound scan showed a lesion measuring 10.5*10.2cm with blood flow; (B and C) On T2-weighted images of MRI revealed a 10.4*11.0*10.8cm mass in the uterine posterior wall, and multiple irregular nodules were observed at the edges and protruded into the lesion; (D) The HRCT scan of the chest on July 23, 2022, showed multiple nodular hyperdensities in both lungs.The largest one about 12 mm*10 mm in size located in the right upper lobe; (E and F) The scan of preoperative HRCT showed multiple nodules in both lungs.A 11 mm nodule in the right upper lobe exhibited an empty bubble within it.(G) The HRCT scan of chest showed multiple soft-tissue densities of both lungs under the pleura which the largest one about 55*34 mm in size located in the subpleural region of right middle lobe.(H) Multiple nodular hyperdensities were revealed in both lungs.The largest one measuring approximately 8mm in diameter located in the left lower lobe.HRCT = high-resolution computed tomography, MRI = magnetic resonance imaging.

Figure 2 .
Figure 2. Surgical specimen: (A) The gross view of hysterectomy specimen: (B) The uterus was dissected through an anterior wall incision showing the grayred, friable mass visible inside.

Table 1
Overview of the English literature on uterine primary epithelioid trophoblastic tumor with metastasis or extrauterine epithelioid trophoblastic tumor.